Reducing the Burden of Neonatal Brain Injury:Assessment of Hypothermic & Melatonin Neuroprotection in an Inflammation-Sensitised Piglet Asphyxia Model

出生时出现的问题会导致婴儿缺氧，可能会导致被称为新生儿脑病的大脑功能紊乱，这可能会导致长期的脑损伤和脑瘫。最近的研究强调了身体对有害刺激(如细菌和受损细胞)的反应的关键重要性，以及这种反应如何放大随后对缺氧的反应。细菌可能存在于婴儿的胎盘或脐带中；这些细菌的存在已被证明增加了发生严重新生儿脑病和儿童后期异常结局的机会。尽管患有新生儿脑病的降温婴儿被证明具有保护作用，但现在有一些研究表明，当身体对细菌产生反应时，这种保护可能会减少或消失。这可能是因为冷却会导致抵抗感染的细胞功能失调或瘫痪。在对体内的细菌已经有反应的情况下，可能还有其他更具保护性的药物。其中一种药物是褪黑素，它是松果体分泌的一种自然荷尔蒙。在高剂量下，我们已经证明褪黑素在缺氧的情况下可以保护大脑。其他研究表明，在身体对细菌和缺氧都有反应的情况下，褪黑素可以保护大脑和身体。在未来，为了给患有新生儿脑病的婴儿正确的药物，重要的是试图找出婴儿是否仅仅因为缺氧而患有新生儿脑病，或者是否有缺氧和对体内、胎盘或脐带中的细菌的反应的组合。我们需要尝试在婴儿出生后的头几个小时内，在血液中找到能给我们这个想法的标志物。我们在伦敦大学学院研究了近20年的纯缺氧仔猪模型。我们现在希望调整这一模型，以反映世界各地分娩病房中出现的新生儿脑病的类型。要做到这一点，我们需要调整小猪模型。我们计划进行三项相关研究：研究1：我们希望建立这一新模式。为了复制人体对细菌的反应，我们将注射一种名为脂多糖(LPS)的物质，这是一种在革兰氏阴性细菌外膜中发现的分子，它能引起强烈的免疫反应。在缺氧期前4小时开始注射脂多糖(整个实验期间2微克/公斤推注和1微克/公斤/小时输注)。因为我们知道内毒素会增强身体对缺氧的反应，我们需要缩短缺氧的持续时间，以确保我们比较的是相似的损伤水平(纯缺氧和内毒素加缺氧)。研究2：我们将比较降温和褪黑素的相对保护反应。我们将测量免疫反应性，看看这是否与两种模型的脑保护有关。研究3：我们将探索能为我们提供更多有关新生儿脑病婴儿脑损伤性质和程度的测试。目前，还没有床边测试可以可靠地预测结果，以及是否存在纯缺氧或混合细菌以及身体的反应和缺氧。简单的血液测试将是一个有吸引力的选择。最近，在脑损伤后的血流中发现了血液中的化学物质，包括被称为microRNAs的遗传片段，这些化学物质可能表明了损伤的程度。因此，我们计划在我们的仔猪模型中使用最先进的技术来开发一组化学物质，这些化学物质可以在一次血液测试中一起测量，以预测大脑损伤的程度。这些研究将使未来能够为特定婴儿量身定做神经保护治疗，并改善世界各地新生儿脑病的预后。

Problems around the time of birth causing a lack of oxygen to the baby can cause disordered brain function called neonatal encephalopathy, which can result in long-term brain damage and cerebral palsy. Recent studies emphasise the critical importance of the body's response to harmful stimuli such as germs and damaged cells and how this response then amplifies the subsequent response to lack of oxygen. The germs may be present in the placenta or umbilical cord of the baby; the presence of these germs has been shown to augment the chance of developing severe neonatal encephalopathy and an abnormal outcome later in childhood. Although cooling babies with neonatal encephalopathy has been shown to be protective, there are some studies which now show that this protection may be less or absent when the body has mounted a response to germs. This may be because the cooling leads to cells that fight infection becoming dysfunctional or paralysed. There may be other medicines that are more protective in situations where there is already a response to germs in the body. One such medicine is melatonin, which is a natural hormone secreted by the pineal gland. In high doses we have already shown that melatonin protects the brain in situations where there is a lack of oxygen. Other studies have shown that melatonin protects the brain and body in situations where there is both a body response to germs and lack of oxygen. In the future in order to administer the correct medicine to babies with neonatal encephalopathy it will be important to try to find out whether a baby has neonatal encephalopathy from just a lack of oxygen or whether there is a combination of lack of oxygen and a response to germs in the body, placenta or umbilical cord. We need to try to find markers in the blood that can give us this idea in the first few hours after the baby is born. We have studied a piglet model of a pure lack of oxygen for almost 20 years at UCL. We now wish to adapt this model to reflect the type of neonatal encephalopathy that presents in the labour ward across the world. To do this we need to adapt the piglet model. We plan to perform three related studies:Study 1: We wish to establish this new model. To replicate the the body's response to germs we will inject a substance called lipopolysaccharide (LPS) which is a molecule found in the outer membrane of gram-negative bacteria and which elicits a strong immune response. We will start the infusion of LPS 4 hours before the period of the lack of oxygen (2micrograms/kg bolus and 1 micrograms/kg/h infusion over the entire experiment). As we know that LPS will augment the body's response to a lack of oxygen we will need to reduce the duration of the oxygen lack to ensure we are comparing similar levels of injury (pure lack of oxygen versus LPS with lack of oxygen). Study 2: We will compare the relative protective response to cooling and melatonin. We will measure the immune responsiveness and see if this is related to the brain protection in both models. Study 3: we will explore tests that will give us more information on the nature and extent of brain injury in babies with neonatal encephalopathy. At present there is no bedside test that can be used to reliably predict outcome and whether there is pure lack of oxygen or a mixture of germs and the body's response and lack of oxygen. A simple blood test would be an attractive option. Recently chemicals in the blood, including genetic fragments called microRNAs, have been found in the blood stream following brain damage and may indicate the extent of the damage. We therefore plan to use state-of-the-art technology in our piglet model to develop a panel of chemicals that can be measured together in a single blood test to predict the extent of brain damage.These studies will allow the future tailoring of neuroprotective treatments to specific babies and the improvement of outcome in neonatal encephalopathy across the world.